The present invention relates to a method and apparatus for switching electronic components into or out of a Radio Frequency (RF), circuit and particularly to a method and apparatus for activating Positive Intrinsic Negative (PIN) diodes.
It is well known in the field of electronics to use one or more diodes to act as switches. By the proper application of a biasing voltage, diodes can be made to conduct or inhibit conduction of RF signals. In such systems, it is frequently desirable that the circuitry which controls the activation and deactivation of the diodes not interfere or otherwise affect the RF being signal communicated.
Often it is desired to use PIN diodes to switch components carrying signals having RF frequencies and high power. The switching of such signals often provides an additional problem of isolation in that the RF energy present in the signal may destructively overload the drive circuits for the PIN diodes. While inductors and chokes have been used for isolation purposes in such circumstances for some RF signals, the use of such inductors in close proximity to the RF signals often results in an unacceptable degradation of the RF signal. Moreover, chokes for signals of high power in the 1.5 to 30 MHz frequency range are generally not practical.
To provide additional isolation, it is known to feed the control wires of the PIN diode drive circuit through a piece of copper tubing which forms the inductive elements of the RF circuit. See, for example, U.S. Pat. No. 4,502,025 to Carl, Jr., et al. The control wires for a particular inductor are withdrawn from the interior of the inductor adjacent its mid-point so that the control wire is at the same RF potential as the inductor being controlled and the circuit is not thereby overloaded. Use of the interiorly disposed control wires presents some difficulties, however, in that there is insufficient room for the many wires in the interior which must be stuffed when many different coils are desired.
It is accordingly an object of the present invention to provide a novel method and apparatus for selectively activating PIN diodes, particularly when the diodes are thousands of RF volts above ground level.
It is another object of the present invention to provide a novel method and apparatus for activating PIN diodes without unnecessary interference in an RF signal being communicated in the associated circuitry.
It is still another object of the present invention to provide a novel method and apparatus for selectively activating electronic elements at high RF voltages without the need for tubing to isolate the control lines.
It is yet another object of the present invention to provide a novel method and apparatus for activating PIN diodes operating at high RF voltages with relatively minor additional stray capacitance in the circuitry.
It is still a further object of the present invention to provide a novel method and apparatus which utilizes VHF power to switch PIN diodes with a relatively high isolation and relatively low capacitance.